Anticyclones and Sea Breezes Flashcards
What are anticylones?
Slow moving features of the atmosphere - they have little or no frontal systems - they are barotropic so little density change - comprised of descending air to cause surface divergence - temperature inversions
What does Barotropic mean?
Little density changes
Define an anticyclone
Large scale circulation of winds around a central area of high pressure (clockwise in N.Hemisphere, anticlockwise in S.Hemisphere)
What is the effect of a temperature inversion in an anticyclone?
Inhibits free convection in the center area
How are subtropical warm core anticyclones formed?
Heating of the earth near the equator forcs upward motion and convection along the monsson trough or ITCZ. The divergence leads to air rising anf moving away from equator aloft. As it moves mid latitudes it cools and sinks, subsiding at the 30 degree parallel of both hemispheres - this is the Hadley cells - the high pressure forms many desert areas.
Explain formation aloft
Anticyclones forming aloft occur in warm core cyclones such as tropical cyclones when latent heat from clouds is released aloft increasing air temperature.
What is oceanic relevance of warm core anticyclones?
Vital for warming the oceans and set up major oceanic gyres
Describe a cold core anticyclone
These are mobile features associate with trough ridge systems and are characterised by cold air descending behind a depression. They are caused by extreme cooling in winter
What is a “block” in meteorology
Large scale patterns in the atmospheric pressure field that are nearly stationary that block or redirect migratory cyclones. AKA blocking highs or blocking anticyclones
What is the effect of a blocking anticyclone
They can remain in place for several days or weeks and cause areas to have same kind of weather for extended time - can distort Rossby Wave patterns
Describe anticyclonic weather
Cloud free in centre - fine and dry in summer - haze trapped under temperature inversion - lack of clouds means cold in winter
How to sea breezes occur (day)
Vertical expansion of the air column during daytime heating tilts isobaric surfaces downward at coast - onshore winds caused at surface and compensating offshore movement aloft.
How do sea breezes occur (night)
At night the air over the sea is warmer and the day time vertical expansion and offshore wind situation is reversed
Sea breeze characteristics
Depth 1km - Temp difference = upper/lower flow - Influence of coriolis should be considered
When will sea breezes be comprimised
Will not form if temperature gradient is not strong enough - can be masked by regional wind - there must be a mechanism for upper air flow to be moved offshore
